Things to build a good hamster home (Eastleigh)

Hi . I adopted a small roborovski hamster last week and bought a cage for him but he does not seem to be happy there. I would like to build a good size home for him and looking for various things like small tree branches/sticks/roots, wood moss, driftwood/ natural wood building bricks/ plywood/ mesh (metal) , leftover air drying clay, leftover Megazorb/ wood shaving/ chinchilla sand/children's play sand/hamster house and a good size fish tank ( does not have to be watertight). I am happy to collect within 20 m radius. Thank you :-)